OBJECTIVES: 1. To compelte a 10-year follow-up study on the low caries prevalence area in N.W. Ohio related to high concentrations of strontium in water supplies. 2. To evaluate the significance of life-long residence and immigration on caries prevalence in children living in the survey towns. 3. To study the possible mechanisms of action of strontium on caries by analysis of samples of plaque, saliva and enamel. METHODS: Children aged 12-14 years old resident in towns of Celina, Coldwater, Delphos, Ft. Recovery, and Portsmouth will be examined for dental caries, OHI, enamel mottling, opacities and pigmentation. Samples of plaque, saliva, surface enamel, and urine will be collected from male 14 year old life-long residents. Samples will be analyzed for strontium (as well as B, Li, Mo, F, Ca, Mg). Plaque samples will also be used for analysis of plaque fluids, bacterial population studies, and plaque activity. Saliva samples collected from the study communities will be tested for their effect on various bacteria.